1. Technical Field
The present invention relates to a bumped IC comprising a light-shielding dummy bump, as well as a display device and an electronic device using the bumped IC.
2. Related Art
In a liquid crystal display device, for example, there is a technique known as chip-on-glass (COG), wherein a driver IC is mounted, without a package, directly on wiring drawn out on the part which is an extension of one of two glass substrates, between which a liquid crystal is encapsulated.
Here, when light enters into an IC chip, the operating voltage changes, for example, to cause malfunction or operation stoppage, and therefore the reliability of the IC is lowered. Especially for an IC chip comprising an analog circuit, the possibility of causing an error in the circuit due to the effect of light is higher than that for an IC chip comprising a digital circuit.
The thickness of a metal wiring layer and a polyimide layer in the IC is 1 μm or less, which do not have a light-shielding effect.
As a conventional light-shielding measure, there are known techniques such as: a configuration to provide a tube-shaped heat-shrinkable film, which has light shieldability, on a mounting unit of an IC chip (Japanese Unexamined Patent Publication No. 11-24605); a configuration to provide a light-shielding layer on a surface (the surface not facing opposite to the glass substrate).of an IC chip or an LCD screen (Japanese Unexamined Patent Publication No. 2001-56478); or a configuration to place a light-shielding sheet member on a surface facing opposite to the mounting surface of an IC chip on a glass substrate (Japanese Unexamined Patent Publication No. 2001-154601).
Mounting a tube-shaped heat-shrinkable film for the purpose of light shielding is complicated and puts a heavier burden on module manufacturers who assemble liquid crystal display devices. Further, in the COG mounting method, the light entered from a side surface of a glass substrate spreads inside the glass substrate and reaches inside an IC chip even if light-reflecting coating is applied on the back surface of the glass substrate.
Therefore, the present invention aims to provide a bumped IC which can surely shield the light at a region to be shielded from the light, as well as a display device and an electronic device using the bumped IC.